Hi all,

I have been working through the RS232 guide on this website and think I have successfully interfaced to my 8052 derivative (ADuC831) using a MAX232EIN chip. Using the code below, I get the same character back from the uC when sending characters to the chip using HyperTerminal just like I should.

$MOD52

CSEG
ORG     0000H

Loop:	
	MOV C,P3.0	
	MOV P3.1,C	
	SJMP Loop

 

When using the section of code below, I get the stream of "U" characters from the uC when connected to it in Hyperterminal like I should.

$MOD52
CSEG

ORG 0000h
	LJMP BEGIN
ORG 40h

BEGIN:
	MOV SCON,#01110000B ; Mode 1/Stop b/Rec en/x/x/Flags
	MOV TH1,#0FDh ; Reload value for 9600 Bd
	MOV TCON,#01010101B ; Fl1/Tim1 on/Fl0/Tim0 on/Ext1-edge/Ext0-edge
	MOV TMOD,#00100001B ; Gate1/Timer/Mode 2/Gate0/Timer/Mode 1

START:
	MOV SBUF,#55H
SERWT:
	JNB SCON.1, SERWT
	CLR SCON.1
	AJMP START

 

However, using the code below, I do not get a character echoed back from my chip while in HyperTerminal like I should.

$MOD52
CSEG

ORG 0000h
	LJMP BEGIN
ORG 40h

BEGIN:
	MOV SCON,#01110000B ; Mode 1/Stop b/Rec en/x/x/Flags
	MOV TH1,#0FDh ; Reload value for 9600 Bd
	MOV TCON,#01010101B ; Fl1/Tim1 on/Fl0/Tim0 on/Ext1-edge/Ext0-edge
	MOV TMOD,#00100001B ; Gate1/Timer/Mode 2/Gate0/Timer/Mode 1
START:
	JNB RI,START
	CLR RI
	MOV A,SBUF
	MOV SBUF,A
	AJMP START

 

Any idea what the problem is? Given the fact that the other two tests work, can the problem still be hardware or do you think it's software? I have looked it over but being fairly new to serial com via a uC, I can't seem to find the problem.

Your advice is appreciated.
Brian